Fifteen common rice maintainer lines and 26 highyielding restorer lines were used to evaluate their thermal resistance and fertility during flowering and early grain filling stages. The rice plants were subjected to high temperature stress at 39-43 ℃ for 1-15 d from main stem flowering. Based on the high temperature stress index, they were divided into thermal resistant lines, semithermal resistant lines, semithermal sensitive lines and thermal sensitive lines. Therefore, the maintainer lines K22B， Bobai B and V20B belonged to thermal resistant lines, whereas Ⅱ32B， Zhongzhe B and Zhong 9B to thermal sensitive lines. The rice restorer line Minghui 63 had the highest thermal resistance, followed by R207, P929, and the lowest thermalresistant P6222， R8006 and P51. The correlation analysis indicated that the high temperature stress index was not significantly correlated with seedsetting rate, abortive grain rate, unfilled grain rate under natural conditions, but significantly correlated with seedsetting rate and unfilled grain rate under high temperature stress. This indicated that high temperature stress occurred during floweringearly grain filling stage mainly decreased the seed setting rate and significantly increased the unfilled grain rate in both rice maintainer and restorer lines.
